Complexes containing 1,8-naphthyridines

Fluorescence Properties of Rare Earth Complexes Containing 1,8-Naphthyridines... 

A detailed study of the infrared spectra of a number of 1,8-naphthyridine-metal complexes has established that the M—N stretching vibrations decrease consistently when the complexes containing a four-membered ring are compared with similar complexes in which the ligand is a,a -bipyridine. Thus, this technique lends itself admirably to the structure determination of these complexes.104,111... 

As for ten coordination, there are no twelve-coordinate complexes containing only unidentate ligands. The most common twelve-coordinate molecules are of the type [M(bidentate)6]. Three structural isomers may be formed by wrapping six bidentate ligands along the edges of an icosahedron (Figme 17). Isomer III is less stable than the other two and is not observed. Isomer I is observed for a number of hexanitrato complexes, for example [La(N03)6] and [Th(N03)6] . Isomer II has been observed for the naphthyridine complex [Pr(napy)6] +. 

Molecular orbital studies on fluxional behavior of metal complexes containing monodentate diimines are of obvious relevance to one-end-off mechanisms for dissociation, as in the classic case of [Fe(bipy)3]. In this approach the behavior of the monodentate diimines is treated alongside that of such diaza-ligands as pyridazine (10), phthalazine (11), and naphthyridine (12)/ ... 

Preformed cationic rhodium complexes containing norbomadiene and different chelating amines based on the bis(l,8-naphthyridine) fragment have also been used as catalysts for these reactions [6S], but the complexes also catalyse the WGSR and there appears no advantage in employing these complex and expensive ligands. 

Ferrarini et al. studied the reaction of 2,6-diamino- and 2-amino-6-acetamidopyridine with different jS-oxo esters in polyphosphoric acid at 80°C (90JHC881). Generally, complex reaction mixtures that contained different bi- and tricyclic products were obtained (see Scheme 7 and Table IX). The products were separated by flash chromatography. In the case of 2-amino-6-acetamidopyridine, the 2,6-diacetamidopyridine 97 was the main product. This compound 97 was also obtained by transamidation in good yield when 2-amino-6-acetamidopyridine was heated in polyphosphoric acid at 80°C. 2-Hydroxy-1,8-naphthyridines 98 were formed in a Conrad-Limpach-type cyclocondensation of 2-aminopyridines and /3-keto ester, while 4-hydroxy-1,8-naphthyridines 99 were probably formed by a ring transformation of 4//-pyrido[l,2-a]pyrimidin-4-ones 100 obtained by the cyclocondensation of 2-aminopyridines and a /3-keto ester. The cyclocondensation of 7-amino-4-hydroxy-l,8-naphthyridine 99 (R = H) and a... 

Complexes with 2,7-dimethyl-1,8-naphthyridine of the formula [233] Ln(2,7-dmnapy)2(N03)3 have been identified containing coordinated nitrate groups C2V symmetry. A coordination number ten for these complexes seems plausible. The IR data for ionic and coordinated nitrate groups are given below. 

In the last decade, complex heterocyclic systems containing a naphthyridine fragment have been synthesized and their reactions giving functionalized naphthyridines have been investigated. The biological activities of naphthyridine derivatives have been studied the most. 

A zinc complex of the BPAN (2,7-bis[2-(2-pyridylethyl)aminomethyl]-l,8-naphthyridine ligand, [(BPAN)Zn2(p-0H)(p-Ph2P02)](C104)2, Fig. 27) catalyzes the transesterification of the RNA model substrate HPNP (2-hydroxypropyl 4-nitro-phenyl phosphate (Fig. 40, bottom) in aqueous buffered solution (HEPES) containing 1% CH3CN.141 The rate of this reaction was found to be 7 times fast than the reaction catalyzed by a mononuclear Zn(II) complex of bpta (Fig. 25). A pH-rate... 

Pyrid-2 -yl)-l,8-naphthyridines containing a carboethoxy group appended at the 4- and 4 -positions were prepared as photosensitizers 360 (Figure 15). Complexation with Ru(II) and NaNCS leads to [Ru (L)2(NCS)2] and subsequent hydrolysis of the ester affords a carboxylic acid dye-sensitizer utilized in solar cells (06IC10131). 

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